The invention relates to a patch antenna for use at microwave wavelengths. (The term "microwave wavelengths" is to be understood to include millimeter wavelengths.)
Microstrip patch antennae are well known. They typically comprise a dielectric substrate with a ground plane on one major surface and, on the other major surface, a strip conductor which provides a feed and which is connected to a broader conductive area known as a patch. The length of the patch (in the direction of the feed) is slightly less than half a wavelength at the operating frequency; the width of the patch may be chosen to provide a suitable radiation resistance.
A suspended patch antenna, in which the patch is supported on a dielectric substrate parallel to and spaced from the ground plane, is also known: see "Analysis of a Suspended Patch Antenna Excited by an Electromagnetically Coupled Inverted Microstrip Feed" by Qiu Zhang et al., Proc. 14th European Microwave Conf., 1984, pages 613-618. Such an arrangement provides the advantages of increased efficiency and bandwidth (see also "Electromagnetically Coupled Microstrip Dipole Antenna Elements" by H. G. Oltman, Proc. 8th European Microwave Conf., 1978, pages 281-285).